whats better
 

i was thinking wouldnt it be better to go twin turbo and use two smaller faster spooling turbos instead of one slower one?
is there enough room for twin turbo?

You need to give some detail of what performance goals you are aimimg for???

A gt35/40 would suit %90+ of peoples HP requirements and you will be hard pressed to find any combination of turbos that would spool faster from lower rpm based on many posts and threads on this forum

Do a search for more details :D